The proposed research will use electron microscopy, immunocytochemistry and radioimmunoassay to specify the complete LH-RH system. Several investigators including the applicant have described this system at the light microscopic level and correlated their findings with radioimmunoassay of isolated components of the system. Thus, preliminary information necessary for a more detailed specification of components of this releasing hormone system is available. (1) Particular emphasis will be placed on studying LH-RH cell bodies in the preoptic area which may influence behavior as well as the release of gonadotropic hormones. (2) A description will be provided of changes in the LH-RH system associated with development. Attention will be focused throughout these studies upon sexual dimorphisms peculiar to this system as represented in maturing normal animals and in animals whose sexual development has been altered by the administration or removal of perinatal hormones. (3) Important extra hypothalamic controlling systems, those of the biogenic amines, interaction with the LH-RH cell bodies and processes will be examined morphologically and immunocytochemically following neurotoxic treatment. (4) Cells which sense circulating levels of steroid hormones and thus modulate gonadotropin secretion and activate behavior will be identified by immunocytochemistry. Interrelationships between these cells and LH-RH cells and processes will be described at light and electron microscopic levels. In analyzing the relationships of both of these systems biogenic amines and steroids to the LH-RH system particular consideration will be given to characteristics that may be distinctive to each sex. (5) In order to further investigate sexual distinctness various conditions leading to or blocking sexual behavior will be used to correlate aspects of this systems with behavior within each sex. (6) Coordinated with this endeavor will be the description or growth hormone-release inhibiting hormine. Correlations of this system with the LH-RH system have been described by the author at the light microscope level. Further delineation and analysis of these elements by EM immunochemistry will be described in relation to LH-RH releasing hormone with special reference to any discernible sexual uniqueness. The core of the proposal centers on Experimental Series 1-3, if time permits the remainder will be investigated.